ObjectivesGender diverse youth face higher risk of engaging in self-injurious thoughts and behaviors (SITBs) compared to cisgender youth. Limitations in past research include a focus on older adolescents, an emphasis on specific gender identity labels that may not be inclusive of the range of youth gender experiences, and reliance on cross-sectional data. Thus, the current study prospectively evaluated dimensions of experienced gender in relation to first-onset SITBs among preadolescents. MethodsData were drawn from the Adolescent Brain Cognitive Development Study, a longitudinal study of youth across the United States. Youth (n = 7909) were aged 10–11 during initial assessment, and follow-up was conducted one year later. Two dimensions of experienced gender, felt-gender incongruence (not feeling aligned with the gender associated with one's sex assigned at birth) and gender non-contentedness (feeling dissatisfaction with the gender associated with one's sex assigned at birth), were assessed. Primary outcomes included non-suicidal self-injury (NSSI), suicidal ideation (SI), and suicide attempts (SA). ResultsLogistic regressions were conducted stratified by sex assigned at birth. For youth assigned female at birth, felt-gender incongruence was prospectively associated with first-onset NSSI and SI and gender non-contentedness was prospectively associated with first-onset of NSSI. For youth assigned male at birth, gender non-contentedness was prospectively associated with first-onset SI. Diverse experienced gender did not prospectively predict SA. ConclusionsDimensions of experienced gender may be associated with subsequent first-onset SITBs among preadolescents. These findings support the need for future research on risk and protective factors that may mediate or moderate this relationship.